Timezone Converter

Pick a date, a time, and a timezone, and see what that instant looks like across a couple dozen major cities and zones at once — for scheduling a call across three continents, working out whether "let's meet at 9" means the same 9 to everyone on the invite, or just double-checking a deploy window doesn't land during someone's 3am.

The distinction that actually causes meeting-scheduling disasters

A UTC offset (UTC+2, UTC-5) tells you the current relationship between a zone and UTC, but it isn't fixed — it shifts with daylight saving in whichever direction that particular region observes it, and plenty of regions don't observe DST at all. This is exactly why "just add 5 hours" reasoning about time differences quietly breaks twice a year for most people who rely on it: the actual offset between two specific places can change independently of each other depending on when their respective DST transitions happen, which don't happen on the same dates worldwide.

Why some offsets aren't even whole hours

India Standard Time is UTC+5:30. Newfoundland is UTC-3:30. Parts of Australia sit at UTC+9:30 or UTC+8:45. These aren't typos or rounding artifacts — they're deliberate historical choices, and they're exactly the kind of thing that breaks naive "add N hours" scheduling logic in code that assumes every timezone offset is a whole number.

The practical rule for anything that has to be reliable

Store and pass timestamps in UTC everywhere in a system — logs, databases, API payloads, message queues — and only convert to a local timezone at the very last step, when actually displaying something to a human. Storing "local time" anywhere in the pipeline is how you end up with subtly wrong data the moment a server, a database, or a client happens to sit in a different timezone than whoever originally wrote the code — a bug that often doesn't surface until months later when someone in a different office looks at the same data and the numbers don't line up.

DST transition dates aren't the same everywhere

The US and EU don't flip their clocks on the same day, and the direction (forward or back) doesn't line up either during the transition weeks — which is exactly the two-to-three-week window every year where "London is 5 hours ahead of New York" is briefly wrong. If you're scheduling something recurring across regions, checking the actual computed conversion for that specific date beats trusting a memorized offset, especially anywhere near a transition.